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// Various tests ensuring that underscore patterns really just construct the place, but don't check its contents.
#![feature(never_type)]
use std::ptr;
fn main() {
dangling_match();
invalid_match();
dangling_let();
invalid_let();
dangling_let_type_annotation();
invalid_let_type_annotation();
never();
}
fn dangling_match() {
let p = {
let b = Box::new(42);
&*b as *const i32
};
unsafe {
match *p {
_ => {}
}
}
}
fn invalid_match() {
union Uninit<T: Copy> {
value: T,
uninit: (),
}
unsafe {
let x: Uninit<bool> = Uninit { uninit: () };
match x.value {
_ => {}
}
}
unsafe {
let x: Uninit<!> = Uninit { uninit: () };
match x.value {
_ => {}
}
}
}
fn dangling_let() {
unsafe {
let ptr = ptr::without_provenance::<bool>(0x40);
let _ = *ptr;
}
unsafe {
let ptr = ptr::without_provenance::<!>(0x40);
let _ = *ptr;
}
}
fn invalid_let() {
unsafe {
let val = 3u8;
let ptr = ptr::addr_of!(val).cast::<bool>();
let _ = *ptr;
}
unsafe {
let val = 3u8;
let ptr = ptr::addr_of!(val).cast::<!>();
let _ = *ptr;
}
}
// Adding a type annotation used to change how MIR is generated, make sure we cover both cases.
fn dangling_let_type_annotation() {
unsafe {
let ptr = ptr::without_provenance::<bool>(0x40);
let _: bool = *ptr;
}
unsafe {
let ptr = ptr::without_provenance::<!>(0x40);
let _: ! = *ptr;
}
}
fn invalid_let_type_annotation() {
unsafe {
let val = 3u8;
let ptr = ptr::addr_of!(val).cast::<bool>();
let _: bool = *ptr;
}
unsafe {
let val = 3u8;
let ptr = ptr::addr_of!(val).cast::<!>();
let _: ! = *ptr;
}
}
// Regression test from <https://github.com/rust-lang/rust/issues/117288>.
fn never() {
unsafe {
let x = 3u8;
let x: *const ! = &x as *const u8 as *const _;
let _: ! = *x;
}
// Without a type annotation, make sure we don't implicitly coerce `!` to `()`
// when we do the noop `*x` (as that would require a `!` *value*, creating
// which is UB).
unsafe {
let x = 3u8;
let x: *const ! = &x as *const u8 as *const _;
let _ = *x;
}
}
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